Sulfur and Sulfate
Dr. Kozet YAPSAKLI
WHAT is sulfur?
Atomic number: 16.
Symbol: S
Native form: is a yellow crystalline (crystal like) solid.
In nature: it can be found as the pure element, and as sulfide and sulfate minerals.
commercial uses: fertilizers, gunpowder, matches, insecticides, fungicides, vitamins, proteins and hormones.
It is critical in the environment, climate and the health of ecosystems.
It’s the tenth most abundant element in the universe
Importance
Drinking water
cathartic effect when present in excessive amounts
EPA secondary standard: should be < 250 mg/L
Public and industrial water supplies:
Have the tendency to form scaling in boilers and heat exchangers
Sewer systems
odor
crown corrosion
SULFATE (continue)
If pH > 8 HS- and S-2 [(H2S) is small] no odor problem
If pH < 8 equilibrium shift right @pH 7 80% H2S
If concentration > 20 ppm toxic
Concentration Levels & Effects
The following table below lists the health effects of exposure to H2S.
Concentration Health Effects
10 ppm Beginning eye irritation
50-100 ppm Slight respiratory tract irritation after 1 hour exposure.
100 ppm Coughing, eye irritation, loss of sense of smell after 2-15 minutes. Altered
respiration, pain in the eyes, and drowsiness after 15-30 minutes followed by
throat irritation after 1 hour. Several hours exposure results in gradual
increase in severity of these symptoms and death may occur within the next
48 hours
200-300 ppm Severe respiratory tract irritation after 1 hour of exposure. Possible
pulmonary edema (fluid in the lungs).
500-700 ppm Loss of consciousness and possibly death in 30 minutes to 1 hour.
700-1,000 ppm Rapid unconsciousness, loss of respiration, and death after 1-3 minutes.
1,000-2,000ppm Unconsciousness at once, loss of respiration and death in a few minutes.
Death may occur even if individual is removed to fresh air at once.
Sulfur Cycle
Sewer Corrosion
High temperature, long detention timessulfate cause crown corrosion in concrete sewers
H2S responsible (indirectly) for crown corrosion
H2S is weaker than carbonic acid little effect on good concrete
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Summary by Example: Pipe Corrosion
organics in sewage are used as energy source to convert SO4 to S= by sulfate reducers (chemoorganoheterotrophs)
S= in equilibrium with dissolved H2S
Dissolved H2S in equilibrium with gaseous H2S
Example Continued
Gaseous H2S dissolves into condensate at crown of sewer pipe and is used as energy source by sulfide oxidizers (chemolithoautotrophs)
As H2S metabolized, acid is produced which dissolves concrete crown causing pipe to collapse
Well ventilation no problem
Crown Corrosion
Hydrogen sulfide corrodes cast iron pipe, valves and fittings:
Hydrogen Sulfide corrodes cast
concrete sewer mains:
Hydrogen sulfide corrodes manhole
and wet well structures:
Methods of Analysis
Ion chromatograph
Formation of insoluable BaSO4
According to the quantity of BaSO4 formation Gravimetric precipitate is weighed
Turbidimetric
Methylthymol blue method
Methods of Analysis (continue)
Gravimetric : > 10 mg/L
Ba+2 + SO4-2 BaSO4
Add BaCl2 in slight access
Acidify w/HCl eliminate BaCO3 ppt
Keep near boiling point
Methods of Analysis (continue)
Excess BaCl2 common ion effect
Formed BaSO4 colloidal form can not be removed by filter
Digestion @ temperature near boiling point crystalline forms
Filter the crystals with special filter
Methods of Analysis (continue)
Turbidimetric method :
Colloidal formation is enhanced in the presence acidic buffer solution
(Magnesium chloride, potassium nitrate, sodium acetate, acetic acid)
Calibration curve
Methods of Analysis (continue)
Automated Methylthymol Blue
Continuous flow analytical instrument
BaCl2 added @low pH BaSO4
pH adjusted to 10
Methylthymol blue added
Methods of Analysis (continue)
Combines with excess Barium blue chelate
Umcomplexed methylthymol blue remaining grey color (automatically measured)